They are not the sort of hat makers whose idea of topping off an outfit involves a charming little cloche or a cozy beret. Some are hell-raising provocateurs while others are more like cheeky jesters full of merrymaking and mischief. A few are die-hard design intellectuals, and at least one literally blurs the boundaries between hats and the hair that they cover. But one thing that unites this motley crew of modern milliners is that “restraint” and “simplicity” are not part of their vocabularies.

“To borrow a phrase from the stylist Simon Foxton, ‘There’s nothing worse than a jaunty trilby,”’ says Fred Butler, an exuberant British accessories designer who got her big break when Lady Gaga’s stylist, Nicola Formichetti, commissioned the now-iconic telephone headpiece for the singer’s music video last year.

“My collections are wearable sculptures that can hang on the wall of your house as a decoration or sling on your body when you want to accessorize a look,” she says. “At the beginning of the design process, I hold up prototypes to my head and, invariably, some of them look like exciting fascinators to my eye.”

While most fascinators are made of delicate feathers or flowers attached to headbands and worn expressly because they are subtler than hats, Ms. Butler’s version of a fascinator could not be more different. Lashings of gold metal corkscrew swirls cascade across the forehead in one piece, while a rainbow of riotous color flanks the ear in clusters of pleated paper wheels and pyramids on another.

According to several industry insiders, the boundaries of hat-making have not been stretched this far for decades. Thanks to a new wave of close-knit and sometimes fiercely competitive young milliners and accessory designers working in cities around the world, flamboyant headgear is no longer just a dramatic flourish confined to the catwalks.

“I’ve been in this business for nearly 30 years, and there have been other waves of statement-making milliners, but this one is somehow more explicit. They are the Schiaparellis of our day,” says Carole Denford, fashion editor of The Hat Magazine, an international millinery trade publication.

Ms. Denford suggests that the last time headgear seemed quite this daring and extravagant was in the 1980s. Although Stephen Jones and Philip Treacy are arguably the most well-known designers from that era, there were others — like Elvis Pompilio, a collaborator of Thierry Mugler’s, and Kirsten Woodward, then Karl Lagerfeld’s milliner at Chanel — who led the way to the decadent designs and radical thinking of today.

It is far too simplistic to dismiss these designers and their successors as “madcap milliners” focused on sartorial shock tactics or creating styling props rather than bona fide hats. But just as Mr. Pompilio and Ms. Woodward sold to leading international department stores, many of today’s young milliners are enjoying moderate commercial success — and at prices that can range from $180 to more than $3,000 a hat.

“Perhaps people have realized the long life of hats. It’s not necessarily a trend-led, seasonal acquisition — it’s an original piece that someone can buy and wear forever, which becomes part of their identity,” says Dolly Jones, editor in chief of the online version of British Vogue. The new generation of milliners has realized, Ms. Jones says, “that, surely, there is money in this idea, too.”

Ms. Denford says that their relevance is being proved not only by what they are achieving at retail but also their influence on wider millinery trends.

“I remember visiting Justin Smith a few years ago and seeing his origami paper-birds hat. Now origami folds are all over the place. It will be the same for Piers Atkinson’s giant cherry motif. I’m sure we’ll see that around soon, too, in watered-down versions,” she says.

Mr. Atkinson, whose quirky collection includes comically absurd fascinators like a glittery eggplant perched above a mesh veil and a matador hat accented with giant roses, says that making what he calls “press pieces” was part of a conscious strategy to introduce the brand before expanding his more commercial range.

What left him stunned, however, was that the more extravagant pieces sold while the “nice hats” got left behind. “We learned a lesson and also realized that there are a lot of customers out there who have the verve and nerve to carry these hats off,” he says.

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Many of the more awe-inspiring designers hail from Britain, where there is a long heritage of hat wearing for formal occasions and a legacy of master milliners like Mr. Jones, Mr. Treacy and Noel Stewart. The creations include the intricate asymmetrical turban caps designed by Mr. Smith at J Smith Esquire, the trompe l’oeil-effect felt hats molded into the shape of a 1920s finger-wave hairstyle by Flora McLean at the House of Flora and the raw brute splendor of sky-high headpieces made of human hair by Charlie Le Mindu.

And the bold, irreverent and experimental spirit of the British has been infectious. Young milliners around Europe include the Irene Bussemaker, based in the Netherlands; Soren Bach from Denmark; Francesco Ballestrazzi of Italy; and Benoit Missolin in Paris.

Others farther afield include Philomena Kwok in Australia, Tomoko Tahara from Japan, Shilpa Chavan from India and Faeth Millinery from the United States.

But why is this global renaissance happening now?

“Chain reaction, maybe?” muses Nasir Mazhar, whose often otherworldly and sometimes downright gritty designs have made him London’s latest golden boy of millinery. “I think hats were an area of style that had been neglected for a long time. People forgot their power. So it started with a few of us.”

Much of the credit, too, probably goes to over-the-top pop stars and divas-in-the-making like Nicki Minaj, Paloma Faith, Shingai Shoniwa and Lady Gaga, who generate invaluable publicity by commissioning hats made to upstage one another in music videos, award ceremonies and concerts.

Ms. Jones of Vogue suggests another explanation: “Perhaps the influence of true fashion tastemakers like Isabella Blow, who determinedly wore extraordinarily artistic creations every day as a matter of course, is infiltrating the more mainstream market these days.”

Indeed after Ms. Blow’s death four years ago, the fashion industry was left with only one high-profile devotee of avant-garde hats, Anna Piaggi. But since then, a dazzling menagerie of fashionistas laced with more than just a streak of idiosyncratic style have settled into the limelight — women like Daphne Guinness, Anna Dello Russo and Susie Bubble, who serve as clients, muses and walking billboards for young milliners.

There also is the growing fascination with an elite group of women who have more occasions than most to wear hats: young aristocrats, royals and posh socialites.

This has been a bumper year of royal weddings — and hats — starting with Prince William and Kate Middleton; Zara Phillips, granddaughter of Queen Elizabeth II; and Charlene Wittstock, now princess of Monaco.

“Perhaps all these weddings have reminded people how a relatively plain or trusted old dress can be transformed with the splash of a colorful hat,” says Ms. Jones.

But lest everyone thinks of jumping on the same theatrical bandwagon, Ms. Butler offers a few sage words of advice on headgear like hers.

“It’s down to whether it’s being worn with ease and conviction or as an affectation. There’s no room for mistake here. Either a hat looks sensational or terrible, which is really down to the wearer and if they are enjoying the experience.”